Characteristics of Cyclones over North-western Pacific Region Yoshio Asuma Division of Earth and Planetary Sciences, Graduate School of Science, Hokkaido University and Akira Kuwano-Yoshida Earth Simulator Center, JAMSTEC

Definition of Explosively Deepening Cyclone (Sanders and Gyakum, 1998) Data Source JMA Global Objectively Analyzed Dataset （ GANAL ） Analyzed Period October 1, 1994 – March 31, 1999 (5 Cold Seasons) Analyzed Region 20  N - 65  N, 100  E  E Deepening Rate  1 Bergeron and Continuing at least 24 hours Slide 1

Explosively Deepening Cyclone Rapid Deepening: Higher Latitude than Higher Latitude than 35  N in Latitude 35  N in Latitude over the Ocean over the OceanFormation: over the Land and Ocean over the Land and Ocean Three Types of Cyclone: 1.Okhotsk – Japan Sea (OJ) Type (OJ) Type 1.Pacific Ocean – Land (PO-L) Type 2.Pacific Ocean – Ocean (PO-O) Type Sea of Japan Sea of Okhotsk Northwestern Pacific Ocean Total : 224 cases Slide 2

Explosively Deepening Cyclone Type TOTAL ： 224 Slide 3

OJ ： 42 PO-L ： 50 PO-O ： 110 OJ TYPE PO-L TYPE PO-O TYPE Rapid Deepening Sea of Japan or Sea of Okhotsk FormationLand Rapid Deepening Northwestern Pacific Ocean FormationLand Rapid Deepening Northwestern Pacific Ocean FormationOcean Slide 4

Deepening Rate Frequency Distribution Maximum Deepening Rate OJ Type Smallest PO-L Type Medium PO-O Type Largest Slide 5

Monthly Frequency of Explosive Cyclones Seasonal Variation OJ Type Late Fall PO-L Type Early and Late Winter PO-O Type Mid-Winter Slide 6

Cyclone Type OJ Type (Late Fall) Short Wave Upper-level Trough Short Jet Streak Weaker Continental Cold Air Mass Extension Extension PO-L Type (Early and Late Winter) Zonally Stretched Jet Stream (Strong Zonal Wind Component) (Strong Zonal Wind Component) Medium Continental Cold Air Mass Extension Extension PO-O Type (Mid-Winter) Strong Jet Stream (Larger Poleward Component) (Larger Poleward Component) Strongest Continental Cold Air Mass Extension Extension Slide 7

Cyclone Type Cold Air Mass over the Continent Upper-level Trough Upper-level Jet ↓ Cyclone Track and Deepening Rate (Cyclone type) Synoptic Environment ↓↑ ↓↑ Cyclone Meso-scale Structure Latent Heat Release Slide 8

Numerical Studies of Extreme Cases Focused on the Latent Heat Release OJ TYPE 00UTC February 27, 1999 (1.84 Bergeron) 00UTC February 27, 1999 (1.84 Bergeron) PO-L TYPE PO-L TYPE 18UTC February 10, 1998 (2.54 Bergeron) 18UTC February 10, 1998 (2.54 Bergeron) PO-O TYPE PO-O TYPE 00UTC December 31, 1997 (2.96 Bergeron) 00UTC December 31, 1997 (2.96 Bergeron) Slide 9

PSU-NCAR MM5 version Horizontal Grid Domain 1 : 200×160 (45 km) Domain 1 : 200×160 (45 km) Domain 2 : 301×271 (15 km) Domain 2 : 301×271 (15 km) Vertical Levels : 23 Sigma level Initial / Boundary Conditions : JMA GANAL Sea Surface Temperature : Reynolds SST Microphysics Domain 1 : Simple Ice Scheme Domain 1 : Simple Ice Scheme (Vapor, Cloud Water, Rain Water, Cloud Ice, Snow) (Vapor, Cloud Water, Rain Water, Cloud Ice, Snow) Domain 2 : Mixed-phase Scheme (+ Supercold Water) Domain 2 : Mixed-phase Scheme (+ Supercold Water) Cumulus Parameterization : Grell’s Scheme Calculation was started before 24 hours from the maximum deepening rate and continued for 48 hours. Sensitivity Experiments CNTL Run : Full Physics CNTL Run : Full Physics DRY Run : No-latent Heat Release DRY Run : No-latent Heat Release Slide 10

OJ TYPE OJ TYPE Back Trajectory ended at 850hPa CNTL 300hPa Winds PV SLP Rain Water Path Precip. WaterDRY 300hPa Winds PV SLP Rain Water Path Precip. Water Slide 11

OJ TYPE DRY CNTL Slide 12

PO-L TYPE CNTL Back Trajectory ended at 850hPa 300hPa Winds PV SLP Rain Water Path Precip. WaterDRY 300hPa Winds PV SLP Rain Water Path Precip. Water Slide 13

PO-L TYPE CNTL DRY Slide 14

PO-O TYPE CNTL Back Trajectory ended at 850hPa 300hPa Winds PV SLP Rain Water Path Precip. WaterDRY 300hPa Winds PV SLP Rain Water Path Precip. Water Slide 15

PO-O TYPE CNTL DRY Slide 16

1.55 Bergeron 0.97 Bergeron 1.24 Bergeron 0.72 Bergeron 2.38 Bergeron 0.71 Bergeron OJ TYPE PO-L TYPE PO-O TYPE CNTL runs show CNTL runs show almost exact cyclone’s almost exact cyclone’s central SLPs (GANAL). central SLPs (GANAL). PO-O cyclone shows PO-O cyclone shows the largest difference the largest difference between CNTL and DRY between CNTL and DRY runs. runs. PO-L cyclone difference PO-L cyclone difference is the next. is the next. Slide 17

OJ TYPE PO-L TYPE PO-O TYPE Late Fall Smallest Deepening Rate Short-wave Upper Trough Weaker Continental Cold Air Mass Extension Upper-level Vorticity Advection Early and Late Winter Medium Deepening Rate Zonally Stretched Jet Stream Medium Continental Cold Air Mass Extension Mid-Winter Largest Deepening Rate Strong Jet Stream Large Continental Cold Air Mass Extension Large Latent Heat Release Effect of Latent Heat SmallestMediumLargest Release Slide 18